Phototube control of grid-glow tubes



18, 1 934. QUARLES 1,984,987

PHOTOTUBE CONTROL OF GRID GLOW TUBES Filed June 10, 1932 INVENTOR law/emcee Quarks,

ATTORN Y Patented Dec. 18, 1934 1,984,987

UNITED-STATES PATENT OFFICE PHOTOTUBE CONTROL OF GRID-GLOW TUBES Lawrence R. Quarles, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 10, 1932, Serial No. 616,481

ll Claims. (Cl. 250-415) My invention relates to translating apparatus An c de bjec of y invention is to p and has particular relation to translating appa-- vide' a translatin syst m in p a n a asratus of the type incorporating gas filled electric filled ec c di c device, and a P discharge devices. sensitive trigger in which the electric discharge An lectric discharge device of the type utidevice shall be normally deenergized when the 5 lized in the practice of my invention ordinarily photo-Sensitive trigger is un a Shall be comprises a cathode of the unexcitable 'or the energized y e application of exciting radiaexcitable ty e, an anode and a control electrode tions to t p t v t ig i su h m all immersed in a gaseous medium, Th d i ner that it shall deliver its maximum output for has substantially two conditions: a deenergized a predetermined excitation f t p t -sensio condition and an energized condition, and'it is live trigger; the Output and e corresponding capable of only abrupt transition Irom one conita n being ay the some for a y pr dition to the other. Potentials are impressed bedetermined System Of Circuit a tstween the principal electrodes of the device and More concisely Stated, it iS an Object of y between its control electrode and its principal invention to provide it translating system of t 15 electrodes and the electrical condition of the deyp incorporating an electric discharge d vice vice is dependent on the relative values of the in Whieh the constants Shall be 50 disposed and potentials. To facilitate explanation in the pres- 50 arranged relative to e ge element that ent case the potential impressed between the y a predetermined small variation f the tri 2J principal electrodes shall be designated as the nt a comparatively lar a io in principal potential and the potential impressed the current p o the c c disc a e debetween the control electrode and a principal Vice Shall be attainedelectrode shall be designated as the control According i10 v invention, I P ide a transpotential lating system incorporating an electric discharge To e h value f principal potential device which is so connected in a circuit with 25 spends a value of control potential which may be an alternating-Current Power pp y u c that termed the limiting control potential. As long the potential impressed b w e the p c pal as thecontrol potential applied to a device reelectrodes is in Opposite phase to the p ial Y mains be1ow t limiting control potential for t impressed between the control electrode and one 33 principal potentials applied the device remains of the P pa ec odes. The potentials are deenergized. However, as soon as a control poof such magnitude that the device is by tential greater than the limiting control potenmaintained in ee ed Cond tion. tial is applied to th devi it t o becomes When it becomes desirable to energize the elecenergized and remains energized, regardless of tile d charge device a tri e t in the 35 changes in th nt potential until t princontrol circuit is so varied that the phase of the 35 cipal potential is reduced to zero or a negative centrol potential is Shifted relative to the D value with reference to the cathode of the device. i- Potential Such a e e that the electric t is an object f my invention t provide a discharge device is energized to deliver substantranslating system of the type incorporating an ally its maximum current Outputelectric discharge device in which the electric novel featufes that I consider characterdischarge device shall be nofmany deenergized lstlc of my lnventlon are set forth with particuand shall be energized to deliver its maximum iarity m the appended i htvention r output by a shift in phase of the control potential i however both: as to Its orgamzatmp and 4 applied thereto, relative) the principal potem ltsmethod of operation, together with additional tial applid obJects and advantages thereof, will best be u A further object of my invention is to provide derstood from the followlng description of specific embodiments when r a translatlng system of the type incorporating the accompanying g g gfigfi with an electric discharge device in which the device Figure 1 is a gm h m t h Shall be a y deehergized. and Shall be p istics of an electric discharge de vice o l llz i'fge ble O being 80 nergized by a Sh t in h Phase utilized in the practice of my invention of the control potential applied thereto relative Fi 2 i a diagrammatic view showing an to the principal potential applied thereto that embodiment of my invention; the device shall deliver its maximum output when Fig. 3 is a vector diagram illustrating the it isso energized. relation between the potentials applied to the 55 as a substantially flat curve 5.

terminals of a system such as is shown in Fig. 2;

Fig. 4 is a diagrammatic view showing a modification of my invention;

Fig. 5 is a diagrammatic view showing another modification of my invention;

Fig. 6 is a vector diagram illustrating the relation between the potentials impressedacross the elements of a system such asis shown in Fig. 5;

Fig. 7 is a diagrammatic view showing a further modification of my invention;

Fig. 8 is a vector diagram corresponding to Fig. 7.

Fig. 9 is a diagrammatic view showing still another modification of my invention; and

Mg. 19 is a vector diagram corresponding to Fig. 9.

In Fig. 1, the potential impressed between the principal electrodes of an electric discharge device, of the type utilized in the practice of my invention, is represented by a sine curve 1, and the control potential is represented by a second sine curve '3, substantially in opposite phase to the first sine curve. As is apparent from the graph the time variable is plotted as abscissa and the magnitude variable is plotted as ordinate. 1

The limiting control potential is represented The principal potential curve 1 to which the limiting control potential curve 5 is related is, as is shown, the central half-cycle '7 of the curve 1 representing the potentials impressed between the principal electrodes. To every point on the half-cycle I of the principal potential curve 1 a point on the limiting potential curve 5 corresponds, and if control potentials are applied which fall above the limiting control potential curve 5, at points corresponding to the principal potential applied, the electric dischargedevice becomes energized.

.If the control potentials fall below this curve,

' that the potential relations as shown in this figwere prevails, the electric discharge device in the system is in ieenergized condition.

As can be seen from the view, the control potential curve 5 is symmetric about the axis 11 of the two half-cycle curves 7 and 9 corresponding thereto, which represent the positive principal potential half-cycle and the negative control potential half-cycle. It is to be noted that if only the magnitude and not the phase of the control potential curve 3 is changed, the control potential curve when it is sufllciently raised may intersect the limiting control potential curve 5 at two points equidistant from the line of symmetry 11, and the output of the system corresponding to one point or the other, will then depend on random conditions of the system. On the other hand, if the phase of the control potential curve 3 is shifted in such manner that the curve moves towards the right a small shift in phase will cause the control potential curve 3 to intersect the limiting control potential curve 5 substantially near the right-hand terminal of the positive half-cycle 7 of the principal potential curve 1, and in consequence thereof, the power output of the electric discharge device, which is a function of the fraction of the positive period during which the electric discharge device remains energized, will be substantially a maximum.

As has been explained hereinabove, the principal object of my invention is to provide a system in which the condition of the electric discharge device is varied by phase shift variation of the control potential, rather than by magnitude variation of this potential, and in which the direction of the shift is such that the output of the electric discharge device is a maximum.

As shown in Fig. 2, the system whereby my invention is practiced comprises an electric discharge device 13, including preferably an. excitable cathode 15, an anode 17 and a control electrode 19, all immersed in a gaseous medium. Power is supplied to the electric discharge device through a power supply transformer 21, the secondary 23 of which is equipped with two terminal taps 25 and 27 and an intermediate tap 29.

The cathode of the electric discharge device 13 is connected to the intermediate tap 29 while the anode 1'7 is connected to one terminal tap through the exciting coil 31 of a relay 33 which symbolizes any load that it may be found desirable to feed through the electric discharge device.

The control electrode 19 of the electric discharge device 13 is connected to the other terminal tap 27 of the secondary 23 through a comparatively high impedance 35, preferably, but not necessarily, a resistor. The terminal taps of the transformer are coupled to a series network comprising a capacitor 37 of comparatively high magnitude and a resistor 39. A photo-sensitive device 41 is connected between the control electrode 19 and the junction-point 43 of the capacitor 37 and resistor 39; the cathode 45 of the device being connected to the control-electrode l9 and the anode 47 being connected to the junction point 43.

The vector diagram corresponding to the circuit of the type shown in Fig. 2 is illustrated in Fig. 3. The potentials applied between the taps 27, 29 and 25 of the secondary 23 are represented by two horizontal vectors 49 and 51. The potential impressed across the resistor 39 that is in series with the capacitor 37 is represented by a vector 53 at a'predetermined angle to the-horizontal vectors, while the potential impressed across the capacitor 37 is represented by a vector 55 at right angles to the vector 53 representing the resistor potential. It will be noted that this representation is in accordance with the physical fact that the individual potentials impressed across the resistor 39 and capacitor 37 are in space quadrature phase relationship with each other.

The potential impressed across the resistor 39 that is connected in series with the capacitor 37 is equal to the sum of the potentials that are impressed across the resistor connected to the control electrode 19 and the cathode of the 39 in series with the capacitor 37, form a right triangle.

It is to be noted that the vector 61 representing the potential impressed between the control electrode 19 and the cathode 15 of the electric discharge device 13 is substantially 180 out 01 phase 'with the vector 51 representing the potential impressed between the principal electrodes 15 and 17 of the electric discharge device 13. The potentials applied to the system are thus substantially represented by the principal potential and the control potential curves 1 and 3 of Fig. 1. For this relative condition of the potentials the electric discharge device 13 is in de-energized condition and remains so unless the condition of the photo-sensitive trigger 41 is disturbed.

However, when the photo-sensitive device 41 is energized from the suitable light-source 63, the vector 61 in Fig. 3 representing the potential impressed between the controlelectrode 19 and the cathode 15 is rotated in a clockwise direction and is represented in its new position by the broken vector 65. It will be noted that this rotation of the vector 61 corresponds to a shift of the control potential in a direction such that the phase difference between the control potential and the principal potential is smaller than it was before the photo-sensitive device 41 was energized. Essentially, therefore, the control potential assumes a condition represented by the broken-line curve 67 in Fig. 1.

- It will be noted that the broken-line curve 67 intersects the limiting control potential curve 51 at a point very near to the left-handterminal of the positive half-cycle '7 of the principal potential curve 1. That is to say, the control potential is now greater than the. limiting potential at a point very near to the beginning of the positive half-cycle of the principal potential. The electric discharge device 13, therefore, becomes energized at this point and remainsenergized during the whole of the positive half-cycle, the maximum of current output being thus delivered by the electric discharge device to the load 33.

In the practice of my invention, the electric discharge device 13 is a mercury-vapor filled device having a cathode 15 of the oxide-coated type and being capableof delivering a maximum crest plate current of 6 amperes anda maximum average plate currentof 4 amperes. The transformer 21 is of a type such that a potential of 220 volts is delivered between each terminal tap 25 and 2'7 and the intermediate tap 29. The photo-sensitive device 41 is of the caesium-oxide cathode highvacuum type. The capacitor 37 has a magnitude of 1 microfarad and the resistor 39 associated therewith has a magnitude of the order of 10,000 ohms. The resistor 35 connected to the control electrode 19 of the electric discharge device 13 has a magnitude of the order of megohms.

In apparatus of the type shown in Fig. 4, the capacitor 37 of the system shown in Fig. 1 is replaced by an inductor 69. It will be noted that by reason of the difference in electrical character between a capacitor and an inductor, the position of the resistor 39 associated with the inductor is now reversed, the resistor 39 being connected where the capacitor 3'? of the system of the type shown in Fig. 2 is connected, and the inductor 69 being connected where the resistor 39 in-the latter system is connected. The vector diagram of the system is the. same as the vector diagram shown in Fig. 3, and the operation of the system is correspondingly similar to the operation of the system shown in Fig. 2.

The apparatus of the type shown in Fig. 5 is different from the apparatus of the type shown in Fig. 2 only by the fact that the resistor 35'associated with the photo-sensitive. device 41 is replaced by a capacitor '71. vThe vector diagram as shown in Fig. 6, is thus only modified to correspond to the fact that since the capacitor 71 and the photo-sensitive device 41 now both have the property of a capacitor, the potential impressed across the two elements, (that is to say, across the resistor 39) is in phase with the potentials impressed across the elements individually. The potential impressed between the control electrode 19 and the cathode 15 is now, as it is for a system of the type shown in Fig. 2, substantially in opposite phase to the potential impressed between the principal electrodes 15 and 1'7 as long as the photo-sensitive device 41 remains deenergized.

However, when the photo-sensitive device is energized, the potential impressed across the capacitor "71 associated with the photo-sensitive device 41 and the potential impressed across the photo-sensitive device 41 no longer remain in phase witheach other and the situation is represented approximately by the broken-lines 73 and '15 as shown in Fig. 6.

However, as in the system of the type shown in Fig. 2, the phase of the control potential is shifted in such a sense that the control potential is brought more nearly in phase with the potential impressed across the principal electrodes.

The apparatus of the type shown in Fig. 7 corresponds to the apparatus of the type shown in Fig. 4 in that the capacitor 37 of the system shown in Fig. 5 is replaced by an inductor 69, and the impedances connected across the terminals 25 and 27 of the supply transformer secondary 23 are suitably repositioned to provide for the difference in the electrical character of an inductor and capacitor. As can be seen from Fig. 8, the vector diagram corresponding to Fig. 7 is similar to the vector diagram shown in Fig. 6 which corresponds to the system shown in Fig. 5.

The system shown in Fig. 9 is ordinarily designated as the reverse system. It is to be noted that this system difiers from the system shown in Fig. 2 by the fact that the photo-sensitive trigger 41 and the resistor 35 are interchanged in position. Corresponding changes may 'also be made in the systems shown in Figs. 4, 5 and '7 to attain corresponding reverse circuits.

In systems of the type shown in Fig. 9 the electric-discharge device 13 is deenergized when the photo-sensitive trigger 41 is excited to a predetermined extent. When the excitation of the photo-sensitive device is sufiiciently decreased, the electric discharge device 13 is energized and delivers substantially its maximum output in the same manner as does the device in the systerns shown in Fig. 1.

In the vector diagram shown in Fig. 10 which corresponds to the circuit shown in Fig. 9 the vector 61 corresponding to the control potential is rotated in a clockwise direction when the illumination impinging on the photo-sensitive device is decreased rather than when it is increased. The broken vector 65 shows its changed position for an increase in excitation of the photo-cell.

It is apparent of course, that the constants utilized in the actual practice of my invention with systems of the type shown in Figs. 4, 5, 7 and 9, may be derived from the constants utilized in systems of the type shown in Fig. 2. The values of the inductors and capacitors are such as to correspond to the. impedance values of the impedances utilized in the apparatus shown in Fig. 2. Thus, the inductor 69, utilized in systems of the type shown in Figs. 4 and 7 is of such magnitude as to correspond to the capacitor 37 utilized in the system of Fig. 2. .On the other hand, the

'sible.

capacitor '71 utilized in the systems shown in Figs. 5 and 7 has a magnitude which is of the order of 25 micro-microfarads to correspond to the 100 megohm resistor utilized in apparatus of the type shown in Fig. 2.

My invention has been shown herein as applied to a particular system and a gas-filled hotcathode electric discharge device 13 of a particular type has been shown as utilized in the practice thereof. It is to be understood that my invention may be equally as well practiced with systems incorporating electric discharge devices of other types, such as mercury-pull devices, having make-alive and keep-alive electrodes, highvacuum electric discharge devices, and cold cathode gas-filled electric discharge devices.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are pos- My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and bythe spirit of the appended claims.

I claim as my invention:

1. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an intermediate tap and-a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said'control electrode and the other terminal tap of said secondary, a plurality of additional impedances, means for connecting said additional impedances between the terminal taps of said secondary, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction point of the impedances that are connected between the terminal taps of said secondary, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said'devic'e thereby to maintain said device in "deenergized condition and means for varying the condition of said lastnamed impedance to shift the phase of the potential impressed between said control electrode.

taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance means for connecting said impedance between said control electrode and the other terminal tap of said secondary, a capacitor and a resistor, means for connecting said capacitor and said resistor between the terminal taps of said secondary, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction-point of the capacitonand resistor that are connected between the terminal taps of said secondary, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition and means for varying the condition of said lastnamed impedance to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

3. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an intermediate tap and a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said secondary, an inductor and a resistor, means for connecting said inductor and said resistor between the terminal taps of said secondary, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction point of the inductor and resistor that are connected between the terminal taps'of said secondary, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition and means for varying the condition of said lastnamed impedance to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

4. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an intermediate tap and a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of saiddevice between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said secondary, a plurality of additional impedances, means for connecting said additional impedances between the terminal taps of said secondary, a photo-sensitive device, said device being normally deenergized, means for connecting said normally deenergized photosensitive device between the control electrode of said device and the junction point of the impedances that are connected between the terminal taps of said secondary, said photo-sensitive device and said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition and means for energizing said photosensitive device to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize'said device.

5. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an in termediate tap and 'a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, a photo-sensitive device, said device being nor mally energized, means for connecting said normally energized photo-sensitive device between said control electrode and the other terminal tap of said secondary, a plurality of impedances, means for connecting said impedances between the terminal taps of said secondary, an additional impedance, means for connecting said additional impedance between the control electrode of said device and the junction point of the impedances that are connected'between the terminal taps of said secondary, said photo sensitive device and said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition and means for deenergizing said photo-sensitive device to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

6. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an intermediate tap and a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance, means for. connecting said impedance between. said control electrode and the other terminal tap oi. said secondary, a plurality of additional impedances connected in series with each other, said series connected impedances being of a type such, that the individual potentials impressed across them when they are connected in series are in time-quadrature phase-relationother, means for connecting said series connected impedances between the terminal taps or said secondary, a further impedance, means for connecting said further impedance between the control electrode of said" device and the junction point of said series connected impedances, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition, and means for varying the condition of said lastnamed impedance to shift the phase of the potentials impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

7. Translating apparatus comprising an electric discharge device including a control electrode ship with each and a plurality of principal electrodes immersed in a gaseous medium, means, including a transformer having a secondary equipped with an intermediate tap and a plurality of terminal taps, for applying potentials between the electrodes of said electric discharge device, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said secondary to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said secondary, a plurality of addi tional impedances connected in series, said seriesconnected impedances being of a type such that the individual potentials impressed across them when they are connected in series are in timequadrature phase relationship with each other, means for connecting said additional impedances between the terminal taps of, said secondary, a photo-sensitive device, said device being normally deenergized, means for connecting said normally deenergized photo-sensitive device between the control electrode of said device and the junction point of said series connected impedances, said photo-sensitive device and said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said device thereby to maintain said device ir deenergized condition, and means for energizing said photosensitive device to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

8. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means for supplying potentials between the electrodes of said electric discharge device, said means having an intermediate tap and a plurality of terminal taps, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said potential supply means to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said potential supply means, a plurality of additional impedances, means for potentials impressed across them connecting said additional impedances between the terminal taps of said potential supply means, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction point of the impedances that are connected between the terminal taps of said secondary, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition and means for varying the condition of said last-named impedance to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

9. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means for supplying potentials between the electrodes of said electric discharge device, said means having an intermediate tap and a plurality of terminal taps, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said potential supply means to maintain a predeter-,v

mined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said potential-supply means, a plurality of additional impedances connected in series with each other, said series connected impedance being of a type such that the individual when they are connected in series are in time-quadrature phaserelationship with each other, means for connect- I ing said series connected impedances between the terminal taps of said secondary, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction point of said series connected impedances, said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in oppositephase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition, and means for varying the condition of said last-named impedance to shift the phase .of the potentials impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

10. Translating apparatus comprising an electric discharge device including a control electrode and a plurality of principal electrodes immersed in a gaseous medium, means for supplying potentials between the electrodes of said discharge device, said means having an intermediate tap and plurality of terminal taps, means for connecting the principal electrodes of said device between a terminal tap and said intermediate tap of said potential supply means to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said potential supply means,

a plurality of additional impedances connected in series, said series-connected impedances being of a type such that the individual potentials impressed across them when they are connected in series are in time-quadrature phase relationship with each other, means for connecting said additional impedances between the terminal taps of said potential supply means, a photo-sensitive device, said device being normally deenergized, means for connecting said normally deenergized photo-sensitive device between the control electrode of said device and the junction point of said series connected impedances, said photo-sensitive device and said impedances cooperating to normally maintain the potential between the control electrode and one principal electrode of said electric discharge device substantially in opposite phase to the potential between the principal electrodes of said device thereby to maintain said device in deenergized condition, and means for energizing said photo-sensitive device to shift the phase of the potential impressed between said control electrode and said principal electrode of said device relative to the potential impressed between said principal electrodes thereby to energize said device.

11. Translating apparatus comprising an electric discharge device including a, control electrode and a plurality of principal electrodes immersed in a gaseous medium, means for supplying potentials between the electrodes of said electric discharge device, and means having an intermediate tap and a plurality of terminal taps, means for connecting the principal electrodes of said device between a terminal tap andsaid intermediate tap of said potential supply means to maintain a predetermined potential between said principal electrodes, an impedance, means for connecting said impedance between said control electrode and the other terminal tap of said potential-supply means, a plurality of additional impedances connected in series with each other, said series-connected impedances being of a'type such that the individual potentials impressed across them when they are connected in series are in time-quadrature phaserelationship with each other, means for connecting said series connected impedances between the terminal taps of said secondary, a further impedance, means for connecting said further impedance between the control electrode of said device and the junction point of said series-connected impedances, and means for varying the condition of one of said impedances, said impedances being so related to each other that when the condition of the last said impedance is varied, the phase of the potential impressed between said control electrode and one of said principal electrodes is shifted between a position in which it is in opposite phase to the potential impressed between said principal electrodes and position in which the potential impressed between said principal electrodes leads the 180, whereby said electric LAWRENCE R. QUARLES. 

